The death toll from an evening explosion in central Tehran rose to two overnight after one person died of his wounds, said Ali Aghamohammadi, Supreme National Security Council spokesman. He said two people remained on the critical list.

Workmen in the southwestern oil city of Ahvaz were repairing water pipes, power lines and buildings damaged in four blasts outside state offices that killed seven people and wounded 70.

Traffic swirled through the streets as normal, but the attacks clearly rattled many Iranians ahead of Friday's polls.

"I'm not going to vote. I'm afraid of another explosion. I think Friday will be a very dangerous day," said Ahmad Ali Yacoub, a 36-year-old government employee in Ahvaz.

Opinion polls show experienced pragmatist Akbar Hashemi Rafsanjani leading in the race to replace outgoing reformist President Mohammad Khatami, who failed to overcome hardline resistance to reform during his eight years in office.

Despite widespread disenchantment among Iran's youthful population of 67 million, interest in the race has picked up with the reinstatement of reformer Mostafa Moin and the conservative vote split betweeen five contenders.

Iranian leaders have been urging a high turnout as a slap to domestic and foreign critics of restrictive electoral laws.

A survey by state broadcaster IRIB published on Monday reported that 73 percent of the electorate definitely planned to vote and another 6 percent would probably do so.

The turnout in last year's parliamentary election was 51 percent and around 67 percent in the 2001 presidential poll.

MAIN RIVALS

"Hardliners were so sure of victory, but it seems to me the main race will be between Rafsanjani and Moin," said Hamid Reza Jalaipour, political science lecturer at Tehran University.

"The reform movement has revived and people who were determined to ignore the elections have now started to think twice about voting, especially after Moin was qualified."

Others, however, blamed groups such as the exiled People's Mujahideen Organisation and foreign agents. "They have done this to create fear and uncertainty among people," Ghodratollah Alikhani, member of parliament's national security and foreign policy commission, told student news agency ISNA.

Rafsanjani, president from 1989 to 1997 and seen as the most moderate of the conservative candidates, remains well short of the 50 percent support he needs to avoid a run-off vote.

A poll published on Saturday showed that Moin, one of three reformists in the race, had edged ahead of former police chief Mohammad Baqer Qalibaf to lie in second place.

The bombings in Ahvaz and Tehran jolted a country where such attacks have become a rarity in the past decade.

About 20 foreign journalists seized by Islamic vigilantes at the scene of the bombing in Tehran were released overnight after being held for about four hours, one of them said.

Two other devices exploded in central Tehran on Sunday evening, causing no casualties, and others were made harmless.

"So far we have defused four bombs in different neighbourhoods," Aghamohammadi said, without saying how they had been found. Some arrests had been made and more were expected.

He said security had been tightened on the border with Iraq, the suspected source of infiltrators, and Iranians should not be afraid to go to the polls.

Some in Ahvaz, like Ahmad Razi, 27, seemed receptive to such reassurances. "Those behind those blasts don't want us to vote. I'm scared, but I'll vote," he said.

Ahvaz is the capital of Khuzestan province, where five people died in ethnic unrest in April. Most of Iran's two million ethnic Arabs live in the Gulf province, which also sits on the bulk of the country's oil reserves.

Rahim Fazilatpour, deputy governor of Ahvaz, said three Arab groups had claimed responsibility for the bombings."